This application claims priority to an application entitled xe2x80x9cMulti-Sectorized Base Transceiver Station Systemxe2x80x9d filed in the Korean Industrial Property Office on Jun. 23, 1998 and assigned Ser. No. 98-23624, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates generally to mobile communication systems and in particular, to a multi-sectorized base transceiver station system in a mobile communication system.
2. Description of the Related Art
A cellular mobile telecommunication system includes a plurality of base transceiver stations (BTSs) for providing mobile communication services to mobile stations that move within a specific area of cell; and a mobile switching center (MSC) connecting the BTSs to a public switched telephone network (PSTN).
The cellular mobile telecommunication system includes technology which enables many subscribers to use the mobile communication services simultaneously by efficiently improving and managing the use of various frequencies among the subscribers. The technology which enables the efficient use of frequencies is primarily cell division technology and sectorization is a main cell division technology. Sectorization entails dividing a sector cell into three equal parts by separating three antennas by 120xc2x0 right and left. The mobile station associates a sector antenna as a BTS.
U.S. Pat. No. 5,428,818 entitled xe2x80x9cMethod and Apparatus For Reducing Interference In A Radio Communication Link of A Cellular Communication Systemxe2x80x9d discloses a technology for serving different service areas (sectors by adjusting the sector antenna of a central communication base site).
FIG. 1a illustrates the structure of a three-sector BTS and FIG. 1b illustrates the service coverage area according to prior art cell-division technology. As illustrated, a first antenna 110 serving sector xcex1 115, a second antenna 120 serving sector xcex2 125, and a third antenna 130 serving sector xcex3 135. The antennas 110, 120, 130 are 120xc2x0 directional antennas separated by 120xc2x0 with respect to each other.
When dividing a cell into sectors using the directional BTS antenna as illustrated by FIGS. 1a and 1b, each antenna supports one-third of the cell, thereby reducing interference by one-third. Accordingly, the total system capacity is increased approximately three times. However, considering the side lobes produced by an electromagnetic wave emitted by an antenna, the efficiency is about 85%, thereby increasing system capacity by approximately 2.55 times.
As stated above, cell division is a method for increasing system capacity by providing coverage areas within a cell where the number of subscribers can be greater than the number of subscribers within the same coverage area without sectorization and with a high level of service quality. However, when available frequency assignments are all being used or the number of subscribers is highly increased, it is possible that the three sectors cannot accommodate all subscribers.
In an effort to solve this problem, if the cell is expanded, a service coverage of the cell decreases and mutual interference tends to increase. Accordingly, it is then necessary to improve system optimization again by further sectorizing the cell by adding additional BTSs and antennas to improve system performance. If this is done, additional costs are realized in system maintenance, such as in renting additional building space for fixing additional mobile communication equipment to the mobile communication system and in purchasing additional BTSs. Therefore, the conventional sectorization technologies cannot increase the number of sectors for increasing system capacity in a mobile communication system without adding additional mobile communication equipment to the mobile communication system.
To solve the problems associated with prior art sectorization technologies, the present invention provides a multi-sectorized base transceiver station system capable of increasing the total number of subscribers which can be simultaneously accommodated in a cell and reducing or foregoing any additional expenses involved in further subdividing the cell.
According to a first preferred embodiment of the present invention, a multi-sectorized base transceiver station system for increasing system capacity in a mobile communication system by sectorizing base transceiver stations covering a particular coverage area within a cell. The multi-sectorized base transceiver station system includes a first base transceiver station having a first narrow beam directional antenna, a second narrow beam directional antenna, and a third narrow beam directional antenna, where the first, second, and third antennas are separated by 60xc2x0 with respect to each other; and a second base transceiver station having a fourth narrow beam directional antenna, a fifth narrow beam directional antenna, and a sixth narrow beam directional antenna, where the fourth, fifth, and sixth antennas are separated by 60xc2x0 with respect to each other. The first base transceiver station and the second base transceiver station are separated by 180xc2x0 with respect to each other.
The first antenna to the sixth antenna have a beamwidth of 45xc2x0 to 60xc2x0. The first antenna and the second antenna have structure of a base transceiver station for an omni-cell, and in particular, for a three-sector cell. The first base transceiver station and the second base transceiver station are located at a site using a single antenna pole for both base transceiver stations.
A second preferred embodiment of the present invention provides a multi-sectorized base transceiver station system for increasing system capacity in a mobile communication system by sectorizing base transceiver stations covering a particular coverage area within a cell. The multi-sectorized base transceiver station includes a first base transceiver station having a first narrow beam directional antenna, a second narrow beam directional antenna, and a third narrow beam directional antenna, where the first, second, and third antennas are separated by 120xc2x0 with respect to each other; and a second base transceiver station having a fourth narrow beam directional antenna, a fifth narrow beam directional antenna, and a sixth narrow beam directional antenna, where the fourth, fifth, and sixth antennas are separated by 120xc2x0 with respect to each other. The first base transceiver station and the second base transceiver station are separated by 60xc2x0 with respect to each other.
The first antenna to the sixth antenna have a beamwidth of 45xc2x0 to 60xc2x0. The first antenna and the second antenna have a structure of a base transceiver station for an omni-cell and in particular, for a three-sector cell. The first base transceiver station and the second base transceiver station are located at a site using a single antenna pole for both base transceiver stations.
A third preferred embodiment of the present invention, provides a multi-sectorized base transceiver station system for increasing system capacity in a mobile communication system by sectorizing base transceiver stations covering a particular coverage area within a cell. The multi-sectorized base transceiver station includes a first base transceiver station having a first narrow beam directional antenna, a second narrow beam directional antenna, and a third narrow beam directional antenna, where the first, second, and third antennas are separated by 120xc2x0 with respect to each other; and a second base transceiver station having a fourth narrow beam directional antenna, a fifth narrow beam directional antenna, and a sixth narrow beam directional antenna, where the fourth, fifth, and sixth antennas are separated by 120xc2x0 with respect to each other. The first and second base transceiver stations are located on a site by equalizing a direction of propagation of the antennas of the first and second base transceiver stations. The first and second base transceiver stations are configured to have a different area of coverage with respect to each other.
The fourth antenna to the sixth antenna are lower along a vertical axis with respect to the first antenna to the third antenna, or the fourth antenna to the sixth antenna having a greater tilt than the first antenna to the third antenna such that the area of coverage of the first base transceiver station is greater or wider than the area of coverage of the second base transceiver station. The first antenna to the sixth antenna have a beamwidth of 95xc2x0 to 120xc2x0, and the first base transceiver station serves a long distance area of the particular coverage area and the second base transceiver station serves a short distance area of the particular coverage area. The first base transceiver station and the second base transceiver station are located at a site using a single antenna pole for both base transceiver stations. The first antenna and the second antenna have a structure of a base transceiver station for an omni-cell and in particular, for a three-sector cell.